Canine influenza virus (CIV) is a recently emerged virus that causes acute respiratory disease in dogs. CIV was first isolated in 2004 from racing greyhound dogs during a respiratory disease outbreak at a Florida racetrack. Subsequently outbreaks were reported at greyhound racetracks and among other breeds of pet dogs. The H3N8 CIV resulted from the transfer of H3N8 equine influenza virus (EIV) to dogs around 1999. These findings were surprising as dogs were thought to be refractory to infection with influenza viruses. Most dogs have no immunity to CIV and infection may therefore spread quickly in any location with concentrated dog populations. Pet dogs are the most popular companion animals living with humans, and may support the replication of multiple influenza virus subtypes and could facilitate the generation of novel virus species with pandemic potential for humans. The true risk of human infection by CIV is unknown as we do not understand the host barriers that restrict human infection.
CIV H3N2 has been previously found in dogs in China, Korea and Thailand, where it has been circulating since it emerged in late 2005. The H3N2 CIV has been recently introduced (2015) in the USA, most likely through the transport of infected rescue dogs from Korea and is now spreading widely in the mid-Western states. This raise concerns about exposure of human in this country, as well as the likely generation of natural reassortants with the H3N8 CIV.
In 2006, the American Veterinary Medical Association (AVMA) called for the urgent development of an effective vaccine against CIV. A vaccine made from inactivated virus have been developed that is administered subcutaneously as two doses to reduce the severity of the CIV disease and to reduce the incidence of CIV infection in naive dogs (Nobivac, Merck). However, to date, no LAIV for CIV infections has been developed. Thus there is a need in the art for improved vaccines for CIV. The present invention satisfies this unmet need.